The field of the present invention is motion isolating systems for mounting devices requiring a stable position.
In the mid-1970""s, mounting systems were developed for motion picture cameras which were used to mount the camera on the body of an operator. These systems were designed to very substantially isolate the motion of the supporting body from the camera. At the same time, the systems provided suspending support for the camera. The supported camera was capable of being lightly guided by the hand of the operator who could move the camera horizontally in all directions either relative to his body or with his body as he moved about. The camera could also be raised or lowered with a relatively light touch. A number of patents have issued on these early systems. They include U.S. Pat. Nos. 4,017,168; 4,156,512; 4,208,028 and 4,394,075. the disclosures of which are incorporated herein by reference.
More recently, refinements to such systems have been considered. Of particular interest is the versatility of the equipment to accommodate different amounts of load. A number of possible load requirements may be contemplated. A trial video image may be desired which would require a relatively light video camera. A much heavier film camera might then be contemplated for the actual image production. Accessories such as stabilizing flywheels, batteries, monitors and the like also may be needed for particular sequences. Thus, a range of support forces can be required.
The performance of such support systems under widely varying load conditions is complex. Through preloading of resilient systems such as springs, the static support weight can be easily accommodated. However, the profile of lifting support across a vertical range of motion can be greatly affected by changes in load. These changes can place the response of the system outside of the acceptable range for operation. Reconfiguration and tuning of the system on location to accommodate such changes in load have been found inconvenient and often unacceptable.
One mechanism which has been devised for adjusting both the load capacity and the profile of load support with vertical motion is disclosed in U.S. Pat. No. 5,435,515, the disclosure of which is incorporated herein by reference. In this system, the support structure geometry is altered through adjustments to the mountings for the resilient force generating elements.
The load to be carried typically includes a tube chassis with a camera platform at the upper end and batteries and other elements at the other. The tube chassis has a handle for manipulating the assembly. A three-axis gimbal mechanism is attached to the tube chassis near but above the center of gravity. The gimbal mechanism is supported by the support system. One such assembly including a tube chassis and three-axis gimbal mechanism is illustrated in U.S. patent application Ser. No. 08/746,204, filed Nov. 6, 1996, now U.S. Pat. No. 5,752,112, the disclosure of which is incorporated herein by reference.
The present invention is directed to a support system used to isolate motion from the load. Four links are pivotally connected to form a structural, articulated arm. Two opposed links include attachments. The other two links are substantially longer than the links with the attachments. A resilient tension cartridge is held at either end to the linkage with one end pivotally held to one of the links and the other end pivotally held to another link. Multiple such arms may be used with such a system in series.
In a first, separate aspect of the present invention, the support system is arranged with one of the tension cartridge ends being pivotally held to a first link longitudinally outwardly of the pivots of that link. The second end of the tension cartridge is pivotally held to a second link which is pivotally joined to the first link. The tension cartridge thus operates outside of the adjoining pivot between the two links. In this way, a high spring rate on the tension cartridge and substantial moment arm variation on the tension cartridge can be effected in a small area.
In a second, separate aspect of the present invention, the tension cartridge includes a canister with a draw bar extending from the canister. A compression spring within the canister is operatively arranged between the draw bar and the canister. Use of a compression spring substantially shortens the cartridge and enables it to be used in association with two adjacent links to take advantage of the high spring rate.
In a third, separate aspect of the present invention, the tension cartridge of the second aspect further includes shims which may be empirically associated with the compression spring to control initial compression forces to avoid substantial bowing. A polymeric anti-friction coating such as PTFE on the inside of the canister as well as such a coating on the spring may be employed to reduce friction, noise and wear in tension cartridge operation.
In a fourth, separate aspect of the present invention, at least one of the longer links includes a tubular body in cross section with an open end. The tension cartridge extends through this tubular body. This arrangement allows the cartridge(s) to be adjusted for pretension or easily replaced to accommodate substantial changes in the weight of the load. The tubular body and the associated attachment arrangement contributes to torsional rigidity as well.
In a fifth, separate aspect of the present invention, a method for reducing friction in a compression spring canister is contemplated. A spring is compressed to observe the direction of lateral bow induced in the spring with compression. One or more shims are added to the end or ends of the spring to resist the bowing under initial compression. The ends of the spring and shims are then effectively nonparallel in the relaxed state. The spring is then introduced into the canister.
In another, separate aspect of the present invention, the combination of any two or more of the foregoing aspects are contemplated to be employed in concert. Further, the use of multiple tension cartridges with an arm and multiple arms linked together are contemplated.
Accordingly, it is an object of the present invention to provide an improved isolating support system and components therefor. Other and further objects and advantages will appear hereinafter.